There are various times at which it is desired to hold bones within a human or animal body in a fixed position with respect to each other. One such situation where it is desired to hold bones together is when performing a sacroiliac fusion. Another situation where it is desirable to hold bones together is after a fracture.
In both of the preceding situations, a screw or other fixation device may be inserted into the two separate bone pieces. The screw thereby holds the bones in a stationary position until bone grows therebetween to thereby fuse the bone pieces together. Such bone growth thereby supplements the strength provided by the bone screw to prevent the bones from moving.
Various bone screws have been developed for use in conjunction with holding bones together. One such bone screw is disclosed in Ray et al., U.S. Pat. No. 4,961,740. The Ray bone screw has a threaded outer surface and an opening formed in a center portion thereof. The opening is adapted to receive bone growth inducing material. The Ray bone screw is particularly adapted for use in conjunction with maintaining adjacent vertebrae in a stationary position with respect to each other as part of a spinal fusion surgical procedure.